Question

For any four vectors a−, b−
, c−, d−
prove
(i) (
a−
×
b−
)
×
(
c−
×
d−
) = [
a−
c−
d−
]
b−
−
[
b−
c−
d−
]
a− and
(ii) (
a−
×
b−
)
×
(
c−
×
d−
) = [
a−
b−
d
]
c−
−
[
a−
b−
c−
]
d−

Answer 1

Answer:

a-,b-,c-,d- =a-b-c-d